Metal deforming – With cleaning – descaling – or lubrication of work or product – Lubricating
Reexamination Certificate
2000-06-05
2001-07-31
Larson, Lowell A. (Department: 3725)
Metal deforming
With cleaning, descaling, or lubrication of work or product
Lubricating
C072S236000
Reexamination Certificate
active
06266985
ABSTRACT:
The present invention relates to a method for improving the lubrication of the edges and ends of pieces to be rolled, particularly hot rolled, said pieces consisting of essentially planar surfaces, such as metal sheets or strips, in order to diminish the wearing of the rolls and reduce the rolling force.
In the hot rolling of metal objects, the friction force between the object to be rolled and the rolling mill pulls the object to be rolled into the rollgap of the rolling mill. Thereafter the friction force is diminished and reaches the value zero at a point where the velocities of the object to be rolled and the rolling mill are equal. In order to make possible the rolling of the object to be rolled, the friction force between the object to be rolled and the rolling mill must be made strong enough. The magnitude of the required friction force is particularly affected by the properties of the object to be rolled. In case the properties of the object to be rolled are changed during rolling, the rolling mills are subjected to additional strain, which further leads to the wearing of the rolling mills.
In hot rolling, such as the hot rolling of stainless steel, the wearing of the rolling mills causes remarkable expenses. A particular problem is the wearing of the edge of the object to be hot rolled, which is for instance a sheet or a strip. On one hand, this is due to the lower temperature of the edge, and on the other hand on the high thermal strength of stainless steel. Moreover, for example in Steckel-type hot rolling, the ends of the object to be hot rolled are cooled, wherefore the rolling force required for rolling the ends is essentially increased; hence the hot rolling process becomes more difficult, and the reduction must be restricted.
Moreover, the wearing of rolling mills leads to the weakening of the quality of the surface of the object to be rolled, in which case part of the rolled product must be classified as scrap. In order to prevent the wearing of rolling mills, there is generally used lubrication, which helps reduce the friction force required in the rolling process. Usually lubrication is applied only in the roll itself.
The object of the present invention is to achieve an improved method for reducing the friction force required for rolling, particularly in hot rolling, by lubricating, apart from the rolls, also the object to be rolled consisting of planar surfaces, at least for the parts that are essential in the rolling process.
According to the invention, the lubrication of the object to be rolled and the roll is advantageously carried out so that while the object to be rolled, essentially consisting of planar surfaces and made of metal, such as stainless steel, is in the rollgap, the medium used for lubrication is applied along the whole edge area of the object to be rolled essentially during the rolling pass, and also at the ends of the object to be rolled, essentially along the whole width of said object. The medium used for lubrication is fed directly onto the surface of the object to be rolled, essentially on that area of said surface where the lubricating medium is advantageously used. The lubricating medium can also be fed onto the roll surfaces, advantageously on that point of the roll which during rolling is in contact with those areas of the object to be rolled where the lubricating medium is advantageously used.
The width of the edge area of the object to be rolled, where the lubricating medium is fed according to the invention, is 5-40%, advantageously 10-30% of the whole width of the object to be rolled. The length of the end of the object to be rolled, where the lubricating medium is fed according to the invention, is 2-20%, advantageously 5-10% of the length of the object to be rolled when measured after each rolling pass. During a rolling pass, the whole object to be rolled passes once through the rollgap, and hence, as the rolling proceeds, also the length where the lubricating medium is fed along the whole width of the object is increased.
According to the invention, the feeding of the lubricating medium onto the surface of the object to be rolled and likewise onto the surface of the roll is advantageously carried out in the proceeding direction of the object to be rolled, by means of at least one feeding device installed in the vicinity of the lubricating medium feeding spot, prior to the roll. The feeding device used for feeding the lubricating medium comprises at least one feeding member, whereby the lubricating medium can be fed onto the desired spot. The feeding of the lubricating medium takes place in connection with the rolling processes, either in continuous or discontinuous operation, essentially depending on the position of the feeding device with respect to the object to be rolled and to the roll.
In a preferred embodiment of the invention, the lubricating medium is fed onto the surface of the object to be rolled, so that at least three feeding members are directed towards each surface to be rolled in said object. The feeding members are mutually positioned so that one is directed to point essentially to the center of the surface to be rolled, whereas the two other feeding members are directed to point towards the edge areas of the object to be rolled, one towards each edge. Furthermore, the feeding members are mutually positioned so that they are connected to the same lubricating medium conduit, in which case the feeding members together constitute one feeding device. The feeding members can also be positioned so that each feeding member is connected to an individual lubricating medium conduit, in which case each feeding member constitutes a separate feeding device. Moreover, the feeding members can also be positioned so that for example the feeding members directed to point towards the center of the object are connected to a common lubricating medium conduit, whereas each of the feeding members directed to point towards the edge areas of the object are connected to individual lubricating medium conduits. The feeding members are advantageously made to operate so that the feeding members directed to point towards the edges of the object to be rolled are in operation essentially throughout the whole rolling pass of said object. On the other hand, the feeding member directed to point towards the center of the object to be rolled is kept in operation only when an end of the object to be rolled or a predetermined area in the immediate vicinity of said end is located in the effective range of the feeding member in question. Consequently, when feeding lubricating medium to the end or to the immediate vicinity of the end of the object to be rolled, the feeding is kept in operation only when starting and finishing the rolling pass. Depending on the width of the object to be rolled, the number of feeding members directed to point towards the center of the object may be one or several, in order to obtain the whole object in the vicinity of the end, essentially along the whole width of said object, within the effective range of the applied lubricating medium.
At least part of the lubricating medium can advantageously be fed onto the surface of the roll located in the rolling mill. Now, in similar fashion as when feeding medium onto the surface of the object to be rolled, towards the roll surface there are directed at least three feeding members which are positioned and made to operate so that the medium can be fed to the edges of the object to be rolled, essentially along the whole length of the object to be rolled, and to the end or to the immediate vicinity of the end of the object to be rolled, essentially along the whole width of the object to be rolled.
The medium nozzles directed towards the edges of the object to be rolled can also be installed so that the feeding members are located essentially on the same level with the object to be rolled. Now the lubricating medium is fed towards the edge of the object to be rolled, wherefrom the medium is spread onto the surfaces to be rolled, defined by the edge of the object to be rolled.
Wh
Huttunen Kari
Kömi Jukka
Levonmaa Raimo
Saxlund Pentti
Larson Lowell A.
Outokumpu Oyj
Smith-Hill and Bedell
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